Federal Signal Corp. unexpectedly disclosed Wednesday that Robert Welding has resigned as the Oak Brook-based company's president and chief executive and that he has been succeeded on an interim basis by board member James Goodwin, the retired former chairman and CEO of United Airlines parent UAL Corp.

Federal Signal, which makes firetrucks, street sweepers, lights for police vehicles and a host of other products used by municipal and governmental customers, didn't offer any explanation for Welding's departure.

Although he already has stepped down from his posts, Federal Signal said Welding will formally retire effective Jan. 1. The company said directors have formed a committee to begin the search for a new CEO. Welding, 59, couldn't be reached for comment.

Welding was an executive vice president with auto parts-maker BorgWarner Inc. before Federal Signal brought him on board as CEO in December 2003. He promptly launched a multiyear restructuring and streamlining effort designed to strengthen the company's profit margins, an effort that has drawn generally good reviews from investors.

But the company's shares have been battered since late October, when Federal Signal announced lower-than-expected third-quarter earnings, reflecting faltering sales at its firetruck segment. The fire engine group had been perceived as strengthening after years of subpar financial performance, and its disappointing operating loss dismayed investors.

In the wake of the company's earnings report, one analyst suggested that although Federal Signal is doing well in many sectors, it remains mired "in the 20th inning of a turnaround."

On Wednesday, the stock closed at $11.51, off 27 cents, on the New York Stock Exchange. That's down 24 percent from the $15.09 the stock commanded Oct. 24, the day before the company reported third-quarter earnings that were half of what Wall Street had expected.

Federal Signal's chairman, James Janning, said Wednesday that the company "appreciate[s] Bob Welding's efforts in repositioning" its business lines. The manufacturer, he continued, is "fortunate" to have access to the services of Goodwin, whom he characterized as "a proven leader with broad management experience."

Goodwin retired as head of the Chicago airline holding company in 2001 after a tumultuous tenure in which he unsuccessfully sought to combine United with rival US Airways Group Inc. and later outraged unionized employees by suggesting the carrier might "perish" if workers didn't grant concessions. He joined Federal Signal's board two years ago.

Goodwin, 63, said in a statement that he plans to "immediately begin working with the board and employees to prioritize initiatives and strengthen and grow Federal Signal."

Analysts surveyed by Reuters Estimates think Federal Signal, which had about 5,600 employees at the end of 2006, will see revenue inch up by just over 4 percent in 2007, to $1.26 billion.